Process for treatment of solid olefin polymers for removal of initiator residues



March 30, 1965 PROCESS FOR `TRA'IMET OF SOLID OLE-FIN POLYMERS FOR REMOVAL oF INITIATOR REsInuEs Filed sept. 25, 1961 J S. SCOGGIN A TTORNE KS" vLL 3,176,000 PROCESS FOR TREATMENT OF SOLID OLEFHN POLYMERS FUR REMOVAL F INITIATOR RESIDUES Jack S. Scoggin, Bartlesville, Ghia., assigner to Phillips Petroleum Company, a corporation of Delaware Filed Sept. 25, i961, Ser. No. M9526 9 Claims. (Cl. '26o-93.7)

'I'his invention relates to the process and apparatus for treatment of solid olelin polymers for removal of initiator residues.

The polymerization of l-oletins in the presence of initiator systems comprising a heavy metal component, such as titanium trichloride or a titanium trichloridealuminum trichloride complex, and an organometal, such as triethylaluminum or diethylaluminum chloride, is well known and the polymers thus produced have found numerous uses. This polymerization method produces a polymer which contains a residue of the initiator system, this residue comprising the heavy metal and halogen which are bound, in some way, in the polymer. For some applications, the presence of this initiator residue is not objectionable but, in other cases, it is necessary that it be removed. For instance, these residues tend to react with some antioxidants used in such polymers to form discolored products. Halogen residues tend to cause corrosion of metal parts used in handling the polymers, such as molding.

An object of this invention is to provide an improved process for treating solid polymers to remove these initiator residues. A further object of this invention is to pro- `vide apparatus suitable for use in this process.

Other objects and advantages of this invention will be apparent to those skilled in the art upon reading this application which includes a drawing showing schematically apparatus suitable for carrying out this process.

Broadly, the invention resides in a process for removing organometal initiator residue from a solid olefin polymer using iirst, second, and third cyclone separation zones, comprising slurrying the polymer containing the initiator residue with a hot extractant which will remove the residue but is not a solvent for the polymers, passing the slurry to a irst cyclone separation zone, removing an overow from said iirst cyclone separation zone, mixing slurry obtained from the lower end portion of said rst cyclone separation zone with the overflow from said third cyclone separation zone and passing this last mixture to said second cyclone separation zone, removing an overflow from said second cyclone separation zone, mixing slurry obtained from the lower end portion of said second cyclone separation zone with an additional portion of said extractant and passing this last mixture to a third cyclone separation zone, mixing slurry obtained from the lower end portion of said third cyclone separation zone with an additional portion of said extractant and passing this last mixture to a filter zone, removing liquid from said ilter zone, removing solid polymer from said lter zone, and drying said polymer.

In another aspect, the invention resides in the combination of apparatus components suitable for carrying out the above process.

Suitable l-oleiins whose polymers can be treated according to this invention include those having 2 to 8 carbon atoms per molecule including ethylene, propylene, l-butene, l-pentene, Z-methyl-l-butene, Z-methyl-l-pentene, 4-methyl-l-pentene, `3,3-dimethyl-l-butene, 3,3-dimethyl-l-hexene, and the like. Mixtures of 2 or more monomers can be used in the polymerization. Many polymerization systems have been disclosed for the polymerization of these monomers. I believe that my United States Patent O 33,176,000 Patented Mar. 30, 1965 invention will find its greatest use. in the treatament of polymers from polymerization system which frequently produce a polymer having a high proportion of initiator residue. For instance, inthe mass polymerization of propylene, the monomer is liquefied and contacted in a reaction zone with a two or more component initiator system wherein one component is an organometal or metal hydride compound of a metal of Groups I, II or III of the Periodic System and another component is a compound of a metal of Groups lV-A or V-A of the Periodic Table. Since there is no extraneous diluent present, the polymer, in some instances, contains a larger quantity of initiator residue than when the same system is used in the presence ot a solvent or diluent. However, the polymer treated by the system of my invention can be prepared by a solution process or by vapor phase or slurry operation.

Suitable organometal compounds include organometal compounds of mono, dior trivalent metals of Groups l, Il or lll, particularly aluminum, gallium, indium, beryllium, sodium, potassium, lithium, rubidium, cesium, magnesium, cadmium, mercury, zinc, barium, or these compounds wherein one or more, but not all, of the hydrocarbon groups is replaced by hydrogen or halogen. The organo groups can be quite large, compounds being applicable which have 15 or more carbon atoms in each alkyl, cycloalkyl or aryl group, and 40 carbon atoms or more in the molecule. Specific examples of such organometal compounds include trimethylaluminum, triethylaluminum, triisobutylalurninum, a mixture of diethylaluminum chloride and ethylalumium dichloride, sometimes referred to as ethylaluminum sesquichloride, diethylaluminum hydride, ethylaluminum dichloride, or diethylaluminum chloride, taken alone, trioctylaluminum, tridodecylaluminum, triphenylaluminum, triphenylgallium, diphenylberyllium, dicyclohexylberyllium, cyclohexylzinc iiuoride, methylaluminum dichloride, dimethylalumnum chloride, dibutylaluminum bromide, octylaluminum diiodide, dipropylgallium liuoride, dicyclohexylgallium chloride, phenylgallium dibromide, eicosylgallium dibromide, tetradecylgallium uoride, diphenylindium chloride, octylindium diluoride, cyclohexylindium dibromide, methylberyllium bromide, and the like.

The metal hydrides can include, as specific examples, aluminum hydride, lithium aluminum hydride, barium hydride, gallium hydride, indium hydride, sodium aluminum hydride, and potassium beryllium hydride,

The compounds of the metals of Groups lV-A and V-A ofthe Periodic System include the oxides, hydrides, halides, oxyhalides and salts of organic acids, usually having 20 or less carbon atoms, such as formic acid. It is usually preferred to employ compounds of titanium, zirconium, hafnium, thorium, vanadium, niobium and tantalum. Of the various compounds, it is generally preferred to employ the titanium halides, including the chlorides, lluorides, bromides and iodides, particularly the 'triand tetrachlorides, the triand tetrabromides, and the triand tetraiodides of titanium, a particularly preferred species being titanium trichloride.

for thermal and oxidative stabilization and the like.

For instance, it has been found that polypropylene stabilized with phenolic type stabilizers, such as 4,4-thio-bissnr/aoco (-tert-butyl-m-cresol) are particularly susceptible to color change during molding at elevated temperatures. This color change has been found to be proportional to the amount of titanium present in the polymer with as little as 25 ppm. causing a color change from a translucent white .to a rust brown. Surprisingly, it has been found possible by the method of this invention to reduce the titaniumcontent to a range at which this darkening is not a problem.

The treating agents used in my processes are materials which are extractants -for 4the iniator residue but in which the polymer is substantially insoluble at the conditions of treatment. Suitable extractants include l to 5 carbon aliphatic alcohols, carboxylic acids and hydroxy-substituted carboxylic acids containing from 2 to 20 carbon atoms per molecule, anhydrides of said acids, and mixtures thereof.

The alcohols include methyl alcohol, ethyl alcohol, both propyl alcohols, and the various butyl and pentyl alcohols. Methyl and isopropyl alcohol are preferred.

Examples of suitable acids are acetic, propionic, nbutyric, isobutyric, valerio, caproic, heptanoic, and caprylic acids.

Solid carboxylic acids can be used when a suitable solvent therefor is included. Typical examples are undecylenic, lauric, palmitic, and arachidic acids; oxalic, malonic, succinic, glutaric, and adipic acids; phenyiacetic, hydrocinnamic acid and benzoic acids.

It is preferred .that the treatment of my invention be carried out before the Ipolymer is contacted with water or air although traces of water can be tolerated.

The treatment should be carried out at a temperature below the agglomeration point of the polymer and under suitable conditions such that the treatment is carried out with all materials in liquid phase until the iinal drying operation. These conditions will vary for the particular polymer being treated and the particular treating agent Y Vused. The a glomeration point can be determined by immersing small particles of the polymer in the treating agent and slowly elevating the temperature until the polymer particles agglomerate. The preferred temperature limit is at least 5 F. 'less than this agglomeration temperature.

The process of my invention can probably be best understood from the study of the drawing which comprises a single tigure. The principal apparatus elements shown on this drawing include a slurry tank 10, a rst cyclone 11, a second cyclone 12, a third cyclone i3, a lter 14., a dryer 15, a fractionation column 16, and a scrubber 17. Slurrytank is provided with an agitator Zion shaft 22 driven by a motor (not shown). Feed conduit 23, having heater 24 therein, extends to and communicates with tank 10. Conduit 26 extends from the lower end portion of tank 10 to the feed inlet ofcyclone 11. Conduit 27V extends from the overflow of cyclone 11 to the inlet of fractionator 16. Communicating with conduit 27 is a conduit 28 adapted to supply additional material to conduit 27. Conduits 29a and 2919 extendy from the slurry outlet of cyclone 11 to the inlet of cyclone l2. Conduit 31 extends from the overow line of cyclone 12 to conduit 23, the connection with conduit 23 being before heater 24. VConduit 32 extends from the overow line of cyclone 13'to conduit 29a. Conduit 3? extends from the slurry outlet of cyclone llZ to the inlet of cyclone 13. Conduit 34 extends from the slurry outlet of cyclone 13 to the feed inlet of lter 14. Conduits 36a and Seb,

` which will be further described hereinafter, communicate with conduit 34 and conduit 37 extends from conduit 36a to lter 14. Conduit 36bis also provided with alcohol makeup conduit 38. Gas supply conduit da also communicates with lter 1d, this conduit extending from conduit 40 whichextends from the upper end portion of knockout drum'39. Removal conduit ill extends from lter 14 topumpfi?. and conduit t3 extends from pump 2. 42 to knockout drum 39. Gas makeup line 44 communicates with conduit 45. Conduit 46, having cooler 47 therein, extends from the lower end portion of knockout drum 39 to conduit d1. Conduit 48 extends from the lower end portion of knockout drum 39 to conduit 33. Screw conveyor dit extends from tilter 14 to dryer 15. Product removal conduit 51 extends from dryer Vi5. Dryer is `also provided with :purge gas supply conduit 52. Conduit 53 extends from dryer 15 to the lower end portion of scrubber 17. Gas removal conduit 54 extends from the upper end portion of scrubber 17 to conduit S2, conduit 52 also communicating with gas makeup conduit 56. Conduit 57, having pump 58 and cooler 59 therein,

, extends to the upper end portion of `scrubber 17 from the lower end portion of scrubber 17.

Fractionator i6 is provided With removal conduitl, having pump d2 therein, which extends to conduit 65 for outlet to drain d3. Recycle line 64 extends from conduit 61 to the kettle of fractionator 1d, this conduit having heater 65 therein. Conduit 67, having condenser 63 therein, extends to accumulator 69. Conduit 71 extends from the lower end portion of accumulator 69 to the upper end portion of fractionator 16. Conduit 7-2extends from the upper end portion of accumulator 69 to a are (not shown). Conduits` 36a and Idb, previously referred to, extend from -line 71 to conduit 34. Conduit 73 extends from .the conduit 57 to conduit 36. Obviously, additional pumps, valves, and the like, will be necessary but, since these do not constitute essential features of my invention, they are not shown.

In the operation of my process, using this apparatus, the polymer from the reactor is mixed, in conduit 23, with the extractant supplied by conduit V31. The amount of extractant should be suiiicient to form a free-owing slurry but the amount is not otherwise critical. This slurry is heated in heater 24 to a temperature of at leastV 200 F., the `upper limit being at least 5 F. lower than the agglomeration point. For polypropylene this temperature range is generally in the range of 200 to 310 F., preferably from 250 to 290 F. This heated slurry is then introduced into slurry tank 10 wherein it is agitatedffor a period of time. This time need not be long, and can range from as little as 1 or 2 minutes up to an hour. Generally 5 to l0 minutes residence time is satisfactory. After a suitable residence time, the slurry is passed through conduit 26 to Vcyclone 11 wherein approximately two-thirds of the extractant is removed overhead and the polymer with the remaining extractant is passed by conduits 29a and 2gb to cyclone 12. The overiiow from cyclone 13 is used to slurry the polymer from cyclone 11, this liquid being supplied through conduit 32. The lliquid removed in cyclone 12 supplies the extractantV for the initial mixing as described above. Y from cyclone 12 is reslurried in the extractant removed from the filter 14 and passed by conduit 33 to cyclone 13. The wet product from cyclone y13 is mixed with puried extractant and the slurry passed to filter 14 wherein it is further Washed. This lter can be one of those wellknown in the art such as a Bird-Young tilter. Inert gas and `air passed through the product to aid in extractant removal and it is believed that this operation is Well known in the art. A screw conveyor 49 conveys the polymer to dryer 15 wherein nal traces of the extractant are removed. This is done by passing an inert gas (nitrogen,

. due gas, etc.) through the polymer to purge final traces of the extractant. This inert gas is introduced by conduit 52 and passes countercurrently rto the polymer which is removed by conduit 51.

The mixture of inert gas and vaporized extractant are removed by conduit 53 and passed to scrubber 17. Cold y extractant is circulated in thisV column ,being removed from the bottom thereof, cooled in heat exchanger 59, and reintroduced into the top. This results in condensation of extractant vapors. The inert gas is removed overhead and returned to dryer 15 by conduits Se and 52.

The wet polymerV The overow from cyclone 11 is passed to -fractionator 16. This fractionator is provided to separate the initiator residue from the extractant. For this purpose, I prefer to add a material which is considerably higher boiling than the extractant, this material being added through conduit 51. 'Ilhe mixture of inert gas and alcohol vapor is removed -by conduit 53 and passed to scrubber `17 operated with a top temperature of F. and a bottom tempera-ture of 133 F., the scrubber being operated at atmospheric pressure.

5 Isopropyl alcohol is removed conduit 28. This permits easier separa-tion and removal from the bottom of this scrubber through conduit 57, of the initiator residue and the added material from the cooled to a temperature of 105 F; and reintroduced into lower end lportion of the column through conduit 61. the top of the scrubber. Uncondensed material is re- The overhead from the column, consisting primarily of moved Vfrom the top of the scrubber and returned by conthe extractant is condensed by heat exchanger 68 and 10 duit S4 to dryer 15. Isopropyl alcohol recovered in the passed to accumulator 69. Non-condensables can .be scrubber is returned to the system through conduits 73 removed by conduit 72 and reux supplied .to the column and 36h. by conduit 71. A material balance for this operation is given in the The following example illustrates my invention and is following table, all amounts being set forth in pounds per considered to be a preferred form thereof. 15 unit time:

Poly- Diethyl- Normal Heavy Propyl- Isopropyl Stream No. propylene T1013 aitilrliin?? decane Alkylate ene Propane Alcohol Inert gas Air Oll 73, 200 112 7 40 0 1, 153 129 0 0 0 32 2 12 0 33 33 500, 000 r 0 0 73, 200 144 9 52 0 1, 497 107 500, 000 0 0 70 111 7 40 0 1, 153 129 330, 200 0 0 73, 33 2 12 0 339 33 113, 300 0 0 i0, 000 7 0 0 0 77 9 500, 200 0 0 33, 130 40 2 12 0 410 47 014, 000 0 0 33, 130 3 0 0 0 77 9 114, 000 0 2 0 0 0 i3 2 500,000 0 0 73, 130 3 0 0 0 i3 2 113,300 0 0 Example As many. possible embodiments can be made of this MS an tot comprising diethylalumnum chloride and titanium tri' 4" inter reted as illustrative and not as undul limitin the chloride was used. The solid polymer was mixed with inveion y g isopropyl alcohol in line 23, heated to 280 F. and stirred I daim m 'slurry tank 1.0 slurry tank ,10 was Operated at 280 1. A process for removing initiator residue resulting F. arid p.s.i.a. The hot slurry was passed to cyclone f rom use of a metal compound wherein the metal is se- 11 and the overiiow introduced into fractionator 16 operatin withato tem erature of F ata ressure of 50 lected from the group consisting of Group IV-A and 15 p sgi a and a Duong temperature of 360 Fp at a pres V-A metals in combination with a compound selected Sure'o'fls Sia A hea alkylate fraction was mixed from the group consisting of organo metals and metal with this olerflow beforevsilntroduction into fractionator hydndes of. Groups I H and In from a Solid Olen 16 The slurry at "a temperature of 165 F was passed polymer using first, second, and third cyclone separation f the lun outlet Ofc done 11 after mhh with the 55 zones, comprising slurrying the polymer containing the Orvoerlow sfmn' c cloe 1g to thein1et`of Cylone 12 initiator residue with an extractant selected from the C clone 13 was oy erated at, a temperature of 120 F and group consistmg of .allphtic E11-Cobol? carboxylic acid? thi material fmmpc Clone 12 was i assed thereto thr'ough and anhydrides of said acids which will remove the resiconduit 33 usin isoyro lalcoholo slurr the same the due but 1S not a solvent for the polymer passing the iso ro l alcohgol leinpy recovered fromylter 14 and 60 slurry to a rst cyclone Separation ZCI-1e removingan .Pedpy.th the Solid gol mer b introduction throu h overflow from sa-id iirst cyclone separation zone, mixing gdutws Substanlu; x ure 80 rop 1 alcohol sug slurry obtained from the 'lower end portion of said rst plied by cmduit 36a is med Wm? they polymer frog! cyclone separation zone with the overflow from said third cyclone separation zone and passing this vlast mixture to 33:3 3333313 3113 33133533533 65 an l 0W rom sai secon cyc one separation zone, mixing uct, con'aingmtg) s1n-1rc 1cliidrieditllclllll,C sslllissgnrcrw slurry obtained'from the lower end portion of said second conv. yat 1 '25 y ht tp l h 1 D ISS P cyclone separation zone with an additional portion of said roa 't t Weltl, geen lciodo.' Iyer t l; extractant and passing this last mixture to a third cyclone ea W1 s eam s emg SPP e m an amoun 0 70 separation zone, mixing slurry obtained trom the lower 720 PmmdS Per hours aff 70 P-s'1"1 TU TemOVe the nal end portion of said third cyclone separation zone with an amount 0f alcohol an merli Purge @as mtfodlfced at the additional portion of said extractant and passing this last downstream end 0f dl'ye' 15 hfouh COHUX $2 at a mixture to a lter zone, removing liquid from said iilter temperature of 250 F. Dry polymer containing less zone, removing solid polymer from said filter zone, and than two parts per million titanium chloride is recoverd in 75 drying said polymer.

2. The process' of claim 1 wherein said extractant is a I`5 carbon alcohol. Y

3f. TheV process of claim 1 wherein said extractant is methyl alcohol.

l4'. The process of claim 1 wherein said extractant is isopropyl alcohol.

5. The process of claim 1 wherein said polymer is a. polymer of a l-olen of 3 to 8 carbon atoms.

6. The process of claim 1 wherein said polymer is polyethylene.

7. The processl of claimr 1 wherein said polymer is polypropylene. l v

8. The' process of claim 1 wherein said initiator residue contains titanium.

9. A process for removing initiator residue resulting from use of a metal compound wherein the metal is selected from the group consisting of Group IV-A and V-A metals in combination with a com-pound selected from the group consisting of organo metals and metal hydrides of Groups I, II, and III from polypropylene using irst, second, and third cyclone separation zones, comprising slurrying polypropylene containing initiator residue with isopropyl alcohol, heating the resulting slurry to a temperature of 280 F. and maintaining said slurry at 280 F. for 5 to 10 minutes, thereafter passing said slurry to a first cyclone separation zone, mixing the overow from said first cyclone separation zone with heavy alkylate and passing the mixture to a fractionation zone, removing a mixture of heavy alkylate and catalyst residue from the lower end portion of said fractionation zone, removing isopropyl alcohol from the upper end portion enf/aoco of said fractionation zone, mixingslurry obtained from the lower end portion of said irst cyclone separation zone with theoverow from said third cyclone separation zone and passing this last mixture to said second cyclone Separation Zone, utilizing the overflow from said second cyclone separation zone as the stream of isopropyl alcohol in the initial slurrying operation, mixing slurry obtained from the lower end portion of said second cyclone separation zone with isopropyl alcohol and passing this last mixture to a third cyclone separation zone, mixing slurry obtained from the lower end portion of said third cyclone separation zone with isopropyl alcohol recovered in said rst fractionation zone and passing this last mixture to a filter zone, removing isopropyl alcohol from said filter zone and utilizing same to mix with ythe slurry removed from said second cyclone separation zone, passing solid polypropylene wet with isopropyl alcohol from said lter zone to a 'drying zone supplied with heated inert gas, removing dry polypropylene from said drying zone, removing a mixture of inert gas and isopropyl alcohol vapor from said drying Zone and passing same to scrubbing zone supplied with cooled isopropyl alcohol wherein isopropyl alcohol is condensedand inert gas is recovered for supply to said drying zone.

References Cited in the le of this patent UNITED STATES PATENTS Horne Nov.'29, 1960 

1. A PROCESS FOR REMOVING INTIATOR RESIDUE RESULTING FROM USE OF A METAL COMPOUND WHEREIN THE METAL IS SELECTED FROM THE GROUP CONSISTING OF GROUP IV-A AND V-A METALS IN COMBINATION WITH A COMPOUDN SELECTED FROM THE GROUP CONSISTING OF ORGANO METALS AND METAL HYDRIDES OF GROUPS I, II, AND III FROM A SOLID OLEFIN POLYMER USING FIRST, SECOND AND THIRD CYCLONE SEPARATION ZONES, COMPRISING SLURRYING THE POLYMER CONTAINING THE INITIATOR RESIDUE WITH AN ETRACTANT SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC ALCOHOLS, CARBOXYLIC ACIDS AND ANHYDRIDES OF SAID ACIDS WHICH WILL REMOVE THE RESIDUE BUT IS NOT A SOLVENT FOR THE POLYMER, PASSING THE SLURRY TO A FIRST CYCLONE SEPARATION ZONE, REMOVING AN OVERFLOW FROM SAID FIRST CYCLONE SEPARATION ZONE, MIXING SLURRY OBTAINED FROM THE LOWER END POTION OF SAID FIRST CYCLONE SEPARATION ZONE WITH THE OVERLFOW FROM SAID THIRD CYCLONE SEPARATION ZONE AND PASSING THIS LAST MIXTURE TO SAID SECOND CYCLONE SEPARATION ZONE, REMOVING AN OVERFLOW FROM SAID SECOND CYCLONE SEPARATION ZONE, MIXING SLURRY OBTAINED FROM THE LOWER END PORTION OF SAID SECOND CYCLONE SEPARATION ZONE WITH AN ADDITIONAL PORTION OF SAID EXTRACTNAT AND PASSING THIS LAST MIXUTRE TO A THIRD CYCLONE SEPARATION ZONE, MIXING SLURRY OBTAINED FROM THE LOWER END PORTION OF SAID THIRD CYCLONE SEPARATION ZONE WITH AN 